highly significantP = 0·0028
A stratified analysis by ethnicity revealed striking differences between Fulani and non-Fulani, with a very high and highly significant heritability estimate in the 135 Fulani (h 2 =0·71, P = 0·0028, likelihood ratio test) and a near zero and nonsignificant one in the 285 non-Fulani (h 2 =0·01, P = 0·49, likelihood ratio test) ( Figure 4 a).